HOME

TheInfoList




A katabatic wind (named from the
Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approximately 10.7 million as of ...
word κατάβασις ''
katabasis Katabasis or catabasis ( grc, κατάβασις, from "down" and "go") is a descent of some type, such as moving downhill, the sinking of the winds or sun, a military retreat, a trip to the underworld, or a trip from the interior of a country dow ...
'', meaning "descending") is a drainage wind, a
wind Wind is the natural movement of air or other gases relative to a planet's surface. Wind occurs on a range of scales, from thunderstorm A thunderstorm, also known as an electrical storm or a lightning storm, is a storm characterized by th ...

wind
that carries high-density air from a higher elevation down a slope under the force of gravity. Such winds are sometimes also called fall winds; the spelling catabatic winds is also used. Katabatic winds can rush down elevated slopes at hurricane speeds, but most are not that intense and many are 10 knots (18 km/h) or less. Not all downslope winds are katabatic. For instance, winds such as the föhn and
chinook
chinook
are
rain shadow A rain shadow is an area of significantly reduced rain Rain is liquid water in the form of drop (liquid), droplets that have condensation, condensed from atmosphere, atmospheric water vapor and then precipitation (meteorology), become he ...

rain shadow
winds where air driven upslope on the
windward 400px, Example image showing definitions of windward (upwind) and leeward (downwind) Windward () is the direction upwind from the point of reference, alternatively the direction from which the wind is coming. Leeward () is the direction downwin ...
side of a mountain range drops its moisture and descends
leeward 400px, Example image showing definitions of windward (upwind) and leeward (downwind) Windward () is the direction ''upwind'' from the point of reference, i.e. towards the direction from which the wind is coming. Leeward () is the direction ''dow ...
drier and warmer. Examples of true katabatic winds include the bora in the
Adriatic The Adriatic Sea () is a body of water separating the Italian Peninsula from the Balkans. The Adriatic is the northernmost arm of the Mediterranean Sea, extending from the Strait of Otranto (where it connects to the Ionian Sea) to the northwest a ...

Adriatic
, the Bohemian Wind or ''Böhmwind'' in the
Ore Mountains The Ore Mountains or Ore Mountain Range () (german: Erzgebirge ; cs, Krušné hory or historically ''Rudohoří'') in Central Europe Central Europe is the central region of Europe. Central Europe includes contiguous territories that are somet ...
, the Santa Ana in southern California, the piteraq winds of Greenland, and the
oroshi is the Japanese term for a wind blowing strong down the slope of a mountain, occasionally as strong gusts of wind which can cause damage. ''Oroshi'' is a strong local wind across the Kanto Plain on the Pacific Ocean side of central Honshu. This te ...
in
Japan Japan ( ja, 日本, or , and formally ) is an island country An island country or an island nation is a country A country is a distinct territory, territorial body or political entity. It is often referred to as the land of an in ...

Japan
. Another example is "the Barber", an enhanced katabatic wind that blows over the town of
Greymouth Greymouth () (Māori language, Māori: ''Māwhera'') is the largest town in the West Coast, New Zealand, West Coast List of regions in New Zealand, region in the South Island of New Zealand, and the seat of the Grey District Council. The populatio ...

Greymouth
in
New Zealand New Zealand ( mi, Aotearoa ''Aotearoa'' (; commonly pronounced by English English usually refers to: * English language English is a West Germanic languages, West Germanic language first spoken in History of Anglo-Saxon Engl ...

New Zealand
when there is a southeast flow over the South Island. "The Barber" has a local reputation for its coldness.


Theory

A katabatic wind originates from radiational cooling of air atop a plateau, a mountain, glacier, or even a hill. Since the
density The density (more precisely, the volumetric mass density; also known as specific mass), of a substance is its per unit . The symbol most often used for density is ''ρ'' (the lower case Greek letter ), although the Latin letter ''D'' can also ...

density
of
air The atmosphere of Earth is the layer of gas Gas is one of the four fundamental states of matter In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (ph ...

air
is
inversely proportional In mathematics Mathematics (from Ancient Greek, Greek: ) includes the study of such topics as quantity (number theory), mathematical structure, structure (algebra), space (geometry), and calculus, change (mathematical analysis, analysis). ...
to
temperature Temperature ( ) is a physical quantity that expresses hot and cold. It is the manifestation of thermal energy Thermal radiation in visible light can be seen on this hot metalwork. Thermal energy refers to several distinct physical concept ...

temperature
, the air will flow downwards, warming approximately
adiabatically
adiabatically
as it descends. The temperature of the air depends on the temperature in the source region and the amount of descent. In the case of the Santa Ana, for example, the wind can (but does not always) become hot by the time it reaches sea level. In Antarctica, by contrast, the wind is still intensely cold. The entire near-surface wind field over Antarctica is largely determined by the katabatic winds, particularly outside the summer season, except in coastal regions when storms may impose their own wind field.


Impacts

Katabatic winds are most commonly found blowing out from the large and elevated ice sheets of
Antarctica Antarctica ( or ) is Earth's southernmost continent. It contains the geographic South Pole and is situated in the Antarctic region of the Southern Hemisphere, almost entirely south of the Antarctic Circle, and is surrounded by the Southern Oc ...

Antarctica
and
Greenland Greenland ( kl, Kalaallit Nunaat, ; da, Grønland, ) is an autonomous territory An autonomous administrative division (also referred to as an autonomous area, entity, unit, region, subdivision, or territory) is a subnational administra ...

Greenland
. The buildup of high density cold air over the ice sheets and the elevation of the ice sheets brings into play enormous gravitational energy. Where these winds are concentrated into restricted areas in the coastal valleys, the winds blow well over hurricane force, reaching around . In Greenland these winds are called piteraq and are most intense whenever a low pressure area approaches the coast. In a few regions of continental Antarctica the snow is scoured away by the force of the katabatic winds, leading to "dry valleys" (or " Antarctic oases") such as the
McMurdo Dry Valleys The McMurdo Dry Valleys are a row of largely Antarctic oasis, snow-free valleys in Antarctica, located within Victoria Land west of McMurdo Sound. The Dry Valleys experience extremely low humidity and surrounding mountains prevent the flow of ...
. Since the katabatic winds are descending, they tend to have a low relative humidity, which desiccates the region. Other regions may have a similar but lesser effect, leading to "blue ice" areas where the snow is removed and the surface ice sublimates, but is replenished by glacier flow from upstream. In the Fuegian Archipelago (
Tierra del Fuego #REDIRECT Tierra del Fuego #REDIRECT Tierra del Fuego#REDIRECT Tierra del Fuego Tierra del Fuego (, ; Spanish for "Land of Fire", formerly also Fireland in English) is an archipelago An archipelago ( ), sometimes called an island group or i ...

Tierra del Fuego
) in South America as well as in Alaska in North America, a wind known as a williwaw is a particular danger to harboring vessels. Williwaws originate in the snow and ice fields of the coastal mountains, and they can be faster than .Williwaw
''weatheronline.co.uk''. Accessed 2013-04-29. In California, strong katabatic wind events have been responsible for the explosive growth of many wildfires, including the 2018 Camp Fire and the 2020 North Complex.


See also

*
Anabatic wind An anabatic wind, from the Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is ...
*
Foehn wind A föhn, also spelled foehn (, ), is a type of dry, warm, down-slope wind that occurs in the lee (downwind side) of a mountain range. It is a rain shadow A rain shadow is a dry area on the leeward side of a mountainous area (away from the win ...
* Valley exit jet *
Bora (wind) The bora is a north to north-eastern katabatic wind in areas near the Adriatic Sea The Adriatic Sea () is a body of water separating the Italian Peninsula from the Balkans. The Adriatic is the northernmost arm of the Mediterranean Sea, extendin ...
* Piteraq


References


Further reading

*Giles, Bill
Weather A-Z - Katabatic Winds By Bill Giles OBE
BBC, Retrieved 2008-10-14 *McKnight, TL & Hess, Darrel (2000). Katabatic Winds. In ''Physical Geography: A Landscape Appreciation'', pp. 131–2. Upper Saddle River, NJ: Prentice Hall. * * *


External links

* {{Authority control Wind Climate of Antarctica Climate of Greenland